Time filter

Source Type


Carruba V.,Paulista University | Huaman M.,Paulista University | Domingos R.C.,National Institute for Space Research | Roig F.,ON
Astronomy and Astrophysics | Year: 2013

Context. Close encounters with (1) Ceres and (4) Vesta, the two most massive bodies in the main belt, are known to be a mechanism of dynamical mobility able to significantly alter proper elements of minor bodies, and they are the main source of dynamical mobility for medium-sized and large asteroids (D > 20 km, approximately). Recently, it has been shown that drift rates caused by close encounters with massive asteroids may change significantly on timescales of 30 Myr when different models (i.e., different numbers of massive asteroids) are considered. Aims. So far, not much attention has been given to the case of diffusion caused by the other most massive bodies in the main belt: (2) Pallas, (10) Hygiea, and (31) Euphrosyne, the third, fourth, and one of the most massive highly inclined asteroids in the main belt, respectively. Since (2) Pallas is a highly inclined object, relative velocities at encounter with other asteroids tend to be high and changes in proper elements are therefore relatively small. It was thus believed that the scattering effect caused by highly inclined objects in general should be small. Can diffusion by close encounters with these asteroids be a significant mechanism of long-term dynamical mobility? Methods. By performing simulations with symplectic integrators, we studied the problem of scattering caused by close encounters with (2) Pallas, (10) Hygiea, and (31) Euphrosyne when only the massive asteroids (and the eight planets) are considered, and the other massive main belt asteroids and non-gravitational forces are also accounted for. Results. By finding relatively small values of drift rates for (2) Pallas, we confirm that orbital scattering by this highly inclined object is indeed a minor effect. Unexpectedly, however, we obtained values of drift rates for changes in proper semi-major axis a caused by (10) Hygiea and (31) Euphrosyne larger than what was previously found for scattering by (4) Vesta. These high rates may have repercussions on the orbital evolution and age estimate of their respective families. © 2013 ESO.

Lim K.,Vancouver | Bly S.,Ottawa | Cargill Y.,Ottawa | Salem S.,ON
Journal of Obstetrics and Gynaecology Canada | Year: 2014

Objective: To assist clinicians in assigning gestational age based on ultrasound biometry. Outcomes: To determine whether ultrasound dating provides more accurate gestational age assessment than menstrual dating with or without the use of ultrasound. To provide maternity health care providers and researchers with evidence-based guidelines for the assignment of gestational age. To determine which ultrasound biometric parameters are superior when gestational age is uncertain. To determine whether ultrasound gestational age assessment is cost effective. Evidence: Published literature was retrieved through searches of PubMed or MEDLINE and The Cochrane Library in 2013 using appropriate controlled vocabulary and key words (gestational age, ultrasound biometry, ultrasound dating). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies written in English. There were no date restrictions. Searches were updated on a regular basis and incorporated in the guideline to July 31, 2013. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. Values: The quality of evidence in this document was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1). Benefits, harms, and costs: Accurate assignment of gestational age may reduce post-dates labour induction and may improve obstetric care through allowing the optimal timing of necessary interventions and the avoidance of unnecessary ones. More accurate dating allows for optimal performance of prenatal screening tests for aneuploidy. A national algorithm for the assignment of gestational age may reduce practice variations across Canada for clinicians and researchers. Potential harms include the possible reassignment of dates when significant fetal pathology (such as fetal growth restriction or macrosomia) result in a discrepancy between ultrasound biometric and clinical gestational age. Such reassignment may lead to the omission of appropriate-or the performance of inappropriate-fetal interventions. © 2014 Society of Obstetricians and Gynaecologists of Canada.

Borikar D.,Walkerton Clean Water Center | Borikar D.,University of British Columbia | Mohseni M.,University of British Columbia | Jasim S.,ON
Water Quality Research Journal of Canada | Year: 2015

Although potential risk of pharmaceuticals and personal care products (PPCPs) and endocrine disrupting compounds (EDCs) and trihalomethanes to humans is small or unconfirmed, it is advisable to remove these wastewater-related contaminants to increase public confidence and acceptance as a precautionary principle and consequently their elimination or reduction during drinking water treatment is warranted. Experiments were conducted using the dual train pilot-scale conventional treatment plant with ozone and ultraviolet/hydrogen peroxide (UV/H2O2) with three different raw water sources. Reductions of trihalomethanes-formation potentials (THM-FPs) were 8–52%. Ozone was found to decrease THM-FPs while UV/H2O2 was found to increase THM-FPs in most of the experiments under experimental conditions. Conventional treatment poorly removed the selected PPCPs and EDCs while ozone þ conventional treatment provided excellent removal. ConventionalþUV/H2O2 treatment also demonstrated effective removal. However, removal of PPCPs and EDCs by conventionalþUV/H2O2 treatment provided lower efficacy for Sites B and C, likely due to the presence of scavengers such as organics, bicarbonates, carbonates and particles. © IWA Publishing 2015.

Brasil P.I.O.,ON | Roig F.,ON | Nesvorny D.,Southwest Research Institute | Carruba V.,Paulista University | And 2 more authors.
Icarus | Year: 2016

Many asteroid families are identified and well characterized all over the main asteroid belt. Interestingly, however, none of them are older than 4. Gyr. Many mechanisms have been proposed to disperse such old primordial asteroid families that presumably have existed, but only very few have really worked. Here we present a plausible mechanism for dispersing primordial asteroid families that is based on the 5-planet instability model known as jumping Jupiter. Using two different evolutions for the jumping-Jupiter model, we have numerically integrated orbits of eight putative primordial families. Our results show that the most important effect on the asteroid families' eccentricity and inclination dispersal is that of the secular resonances, in some cases associated with the mean motion resonances. As for the semimajor axes spreading we find that the principal effect is that of close encounters with the fifth giant planet whose orbit briefly overlaps with (part of) the main belt. Therefore, the existence of a fifth giant planet with the mass comparable with that of Uranus' or Neptune's could contribute in important ways to dispersal of the primordial asteroid families. To have that effect, the interloper planet should go into and considerably interact with the asteroids during the instability phase. © 2015 Elsevier Inc.

Marcucci P.A.,Electrical Safety Authority | Smith S.,ON | Gomez M.,St. Johns Rehab Hospital | Fish J.S.,University of Toronto
Journal of Burn Care and Research | Year: 2010

The purpose of this study was to determine the circumstances of electrical burn injuries caused by the use of multimeters among electricians and electrical apprentices in Ontario and to develop a burn prevention program to reduce them. A survey to investigate electrical injuries caused by multimeters was mailed in June 2004 to 5000 Ontario electricians and electrical apprentices. A high voltage laboratory tested the effectiveness of fused leads to reduce multimeters malfunction. The results of the survey and laboratory tests helped to implement a burn prevention program. Then, a mail fused leads multimeter exchange program was implemented, and proposals to improve the multimeters standard were made to the Canadian Standards Association. Nine hundred (18%) workers responded the survey. There were 801 (89%) electricians, 81 (9%) electrical apprentices, and 27 (3%) with other qualifications. Ninety-nine (11%) had a multimeter fail during use, and half of them suffered critical burns. Causes of the injury were operator error (59%), wrong category rating (21%), defective equipment (18%), and others (2%). More than 2000 electrical contractors acquired the new fused leads multimeters. There were no critical injuries caused by multimeters in the years 2006, 2007, and 2008 (January to August) in Ontario. Understanding the cause of electrical burn injuries by multimeters and engaging members of the integrated electrical safety system in a multifaceted prevention program were effective in reducing electrical burn injuries. Fused leads multimeters proved to be effective in preventing most common user errors and electrical burn injuries caused by multimeters. © 2010 by the American Burn Association.

Discover hidden collaborations